Improved process for bleaching paper-pulp



UNITED STATES Eric@ PATENT IMPROVED PROCESS FOR BLEACHING PAPER-PULP.

Specification forming part of Letters Patent No. 51,569, dated December 19, 1865.

To all 'whom 'it may concern:

Be it known that I, JOHN W. DIxoN, of

the city of Philadelphia and State of Pennsylvania, have invented a new and useful Process for Bleaching Paper-Pulp, applicable especially to pulp made from straw, Wood, or other vegetable fibrous material; and I do hereby declare 'the following to be a full and exact description of the same, reference being had to the annexed dra\ving,which shows one convenient form of apparatus for carrying out my process. Y Heretofore bleaching of the pulp for paper has been conducted in open tubs or vats, and with Warm or cold solutions of chloride lime and acid or with chlorine gas.

My improvement consists in subjecting the material to be pulped to the successive action of dilute acid in a liquid state at a high temperature and pressure in a close digester, and of a solution of hypochlorite of lime (bleaching-salts) in the same digester under pressure.

If desired, the operation can be performed in the same boiler or digester in Which the material has been pulped, after the pulping has been performed.

l prefer the apparatus shown in the annexed sketch, which I have also applied to pulping Wood and other vegtable brous material.

A is a strong iron digester or boiler, having a man-hole and cover, B, and a perforated diaphragm, E, with a central opening and cover, F, and a lower perforated diaphragm, H, With a slide-valve, I, communicating by the tube K with the stuff-chests or grindigigengine.

In the space V is a spiral coil, L M N O P, through which steam or water is to be passed to maintain the heat of the contents of the digester.

A tube, R S T, connects the space in the digester below the diaphragm with the upper part of the digester.

At Y a rotary pump is placed.

W is a tank or receiver in which the solutions are to be placed before passing into the digester.

A branch tube, X, connects the tube T S at S with the bottom of W. There is a cock at lon the tube R S, and oneI at 2 on the pipe X.

There is a discharge-cock at 3 to drain off and empty the liquid in the digester.

The operation is as follows: The material to be bleached is placed in the digester A through the man-hole top and the opening at F. It' the material to be bleached has been previously pulped in the same digester, then it is to be Well Washed out by closing the cock 1, opening the cock Zand the cock 3, and starting the pump c, which will cause the fresh Water in W to be forced up into the top of the digester, and to pass down through the mass and drain off through cock 3. Cock 3 is then closed and a very weak mixture of Water and sulphuric acid-say tivo gallons of acid to about fifteen hundred gallons of Water-is then placed-in the tank W, and this is pumped up by pump c onto the top of the material. After the digester is lled With this acid solution, cock 2 is to be closed, cock l opened, and heat is to be applied, by the steam or hot water coil L M N O P, until the Whole contents are brought to an ordinary boiling heat. The pump c is kept in action,and causes a circulation of the acidulated Water from the bottom to the top of the boiler and through the mass to be bleached. After this circulation has continued for some time-say about one hourthe cock 3 is opened and the acid Water drained oif. The cocks 3 and l are then again closed and the tank Wis filled with a solution of hypochlorite of lime (commonly called chloride of lime7 or bleaching-salts 77) of about to Baume. The pump o, being again started, throws this solution into the top of the digester upon the mass to be bleached. When the digester is filled in this Way the cock 2 is then closed and the cock l opened. The pump then, being continued in action,will force the bleaching-solution to circulate from the bottom to the top of the di gester and through the mass to be bleached. During thisV last operation the heat of the bleachingliquid should be maintained at near or above 3000 Fahrenheit by causing steam or hot Water of the required temperature to pass through the coil L M N O P from any convenient boiler or generator.

I do not design in this specilication to confine myself to this specific form of apparatus, but merely describe it as a good form to carry out my process.

What I do claim as my invention is- 3. Pulping, Washing, and bleaching wood, 1. The process of bleaching pulp by the acstraw, or other vegetable fibrous material in lLion of a solution of chlorine or chloride of the saine digester under pressure.

lime at a high temperature and under pressure. JOHN W. DIXON.

2. Circulatingthebleaching-solution through the mass to be bleached in the digester, While Witnesses highly heated and under pressure, by means J. ROBERTS HOWELL,

Of a pump or its equivalent7 substantially as GEO. BUCKLEY.

above described. 

